Checking my last day of health coverage - 24 weeks in

I was told my coverage ends on my last day, but the letter says the end of the month. I have read a lot of threads here and could not find my exact situation. I do not want to be surprised by a bill. What should I do about appointments?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

Keep a copy of any coverage confirmation in case of later disputes.